<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>Document</title>
		<script type="text/javascript">
		
		/*var age = 28;
		age = 30;
		alert(age);*/
		
		//输出当前变量/常量的数据类型typeof
		var name = "Jacky",age = 30,sex="man";
		// alert(sex);
		alert(typeof name);
		alert(typeof age);
		name = 18;
		alert(typeof name);
		</script>
	</head>
	<body>
	</body>
</html>
